The result left Juventus on 93 points from 35 games, eight ahead of AS Roma with three matches each to play.
Juventus will wrap up the title if they beat Atalanta at home on May 5 or if Roma fail to beat bottom club Catania on Sunday.
Sassuolo are joint 17th with Bologna on 28 points. The bottom three in the 20-team table go down.
"It was a really a difficult game because of the weather, the pitch and Sassuolo who put us under a lot of pressure," Marchisio told Sky Sport Italia.
"This match reflected our season, as we got through with character and determination. We're nearly there."
With a Europa League semi-final second leg against Benfica looming on Thursday, Juventus coach Antonio Conte left Stephan Lichtsteiner and Leonardo Bonucci out of the starting lineup and his side were quickly on the ropes.
Sassuolo, making their top flight debut this season, have already made their mark with a 4-3 win over AC Milan which caused their opponents to sack coach Massimiliano Allegri and replace him with Clarence Seedorf.
In pouring rain, Sassuolo forward Nicolas Sansone sounded an early warning with a shot across goal before Zaza opened the scoring. His angled shot deflected off Angelo Ogbonna and slipped between Gianluigi Buffon and the near post.
The hosts were threatening a second until Juventus took a quick free kick and Tevez rifled home a low, deflected shot.
It would have been the Argentine's 19th goal of the season but Serie A's official website gave it as an own goal by Sassuolo defender Longhi.
With pools of water starting to appear on the pitch early in the second half, Sansone played a neat-one two with Zaza and fired over from the edge of the area as Sassuolo threatened again.
Instead, Juventus went ahead when a clearance out of the Sassuolo defence went straight to playmaker Pirlo, who lobbed a first-time pass over the defence for Marchisio to fire past Gianluca Pegolo.
Juventus wrapped the game up when substitute Lichtsteiner's low cross from the right was cheekily back-heeled into the net by Spaniard Llorente.
- Sports & Recreation
- Claudio Marchisio
- Carlos Tevez
- Andrea Pirlo
- Fernando Llorente
- Alessandro Longhi